Arterial blood monitoring probe

Abstract

This arterial blood monitoring system takes advantage of the basic statistical property that arterial blood contains a plurality of dominant absorbers, whose measured light absorption spectra appear as a constant over a short interval of time. By measuring the transmitted light as it varies with arterial pulsation at selected wavelengths of light, over a common light path, the relative amount of these dominant absorbers in the arterial blood can noninvasively be determined. To ensure the common light path, a sandwich construction light detector is used.

I claim: 
     
       1. A probe for noninvasively measuring components contained in arterial blood in a subject, which components include a plurality of dominant absorbers, by producing data indicative of a change in light absorption as a function of a change in path length in said arterial blood in said subject at a plurality of predetermined wavelengths of light,comprising: a plurality of light source means for transmitting a plurality of beams of light, at a plurality of predetermined wavelengths of light along a substantially identical light path through said arterial blood; and   means for measuring a change in light absorption of said plurality of beams of light transmitted through said arterial blood, indicative of said change in path length at said plurality of wavelengths of light through said arterial blood along said substantially identical light path, comprising: first light detector means for measuring the magnitude of a first of said plurality of beams of light transmitted at a first of said plurality of wavelengths of light along said substantially identical light path:   second light detector means for measuring the magnitude of a second of said plurality of beams of light transmitted at a second of said plurality of wavelengths of light along said substantially identical light path; and   wherein said first and said second light detector means are mounted coaxially along said substantially identical light path.     
     
     
       2. The probe of claim 1 wherein said first light detector means is mounted on top of said second light detector means in a sandwich configuration, wherein said first and second light detector means are coaxial with said substantially identical light path. 
     
     
       3. The probe of claim 2 wherein said second beam of light is transmitted through said first light detector means to said second light detector means. 
     
     
       4. The probe of claim 1 wherein said first light detector means is interposed between said second light detector means and said arterial blood along said substantially identical light path. 
     
     
       5. A probe for noninvasively measuring components contained in arterial blood in a subject, which components includes a plurality of dominant absorbers, by producing data indicative of a change in light absorption as a function of a change in path length in said arterial blood in said subject at a plurality of predetermined wavelengths of light, comprising: a plurality of light source means for transmitting a plurality of beams of light, at a plurality of predetermined wavelengths of light along a substantially identical light path through said arterial blood; and   means for measuring a change in light absorption of said plurality of beams of light transmitted through said arterial blood, indicative of said change in path length at said plurality of wavelengths of light through said arterial blood along said substantially identical light path;   wherein a first and a second of said plurality of dominant absorbers are water and hemoglobin, which contains oxygenated and deoxygenated components, wherein a first light source means produces a first beam of light at a wavelength of approximately 810 nanometers and a second light source means produces a second beam of light at a wavelength of approximately 1270 nanometers, said measuring means comprises:   first light detector means comprising a silicon photodiode light detector responsive to wavelengths of light in and around 810 nanometers;   second light detector means, comprising a germanium photodiode light detector responsive to wavelengths of light in and around 1270 nanometers; and   wherein said first and said second light detector means are mounted coaxially along said substantially identical light path.   
     
     
       6. The probe of claim 5 wherein said first light detector means is mounted on top of said second light detector means in a sandwich configuration, wherein said first and second light detector means are coaxial with said substantially identical light path. 
     
     
       7. The probe of claim 6 wherein said second beam of light is transmitted through said first light detector means to said second light detector means. 
     
     
       8. A probe for noninvasively measuring components contained in arterial blood in a subject, which components include a plurality of dominant absorbers, by producing data indicative of a change in light absorption as a function of a change in path length in said arterial blood in said subject at a plurality of predetermined wavelengths of light, comprising; a plurality of light source means for transmitting a plurality of beams of light, at a plurality of predetermined wavelengths of light along a substantially identical light path through said arterial blood;   means for measuring a change in light absorption of said plurality of beams of light transmitted through said arterial blood, indicative of said change in path length at said plurality of wavelengths of light through said arterial blood along said substantially identical light path;   wherein said first and second dominant absorbers are water and hemoglobin, which contains oxygenated and deoxygenated components, wherein a first light source means produces a first beam of light at a wavelength of approximately 660 nanometers and a second light source means produces a second beam of light at a wavelength of approximately 940 nanometers and a third light source means produces a third beam of light at a wavelength of approximately 1270 nanometers, said measuring means comprises:   first light detector means comprising a silicon photodiode light detector responsive to wavelengths of light in and around 660 and 940 nanometers;   second light detector means, comprising a germanium photodiode light detector responsive to wavelengths of light in and around 1270 nanometers; and   wherein said first and second light detector means are mounted coaxially along said substantially identical light path.   
     
     
       9. The probe of claim 8 wherein said first light detector means is mounted on top of said second light detector means in a sandwich configuration, wherein said first and second light detector means are coaxial with said substantially identical light path. 
     
     
       10. The probe of claim 9 wherein said third beam of light is transmitted through said first light detector means to said second light detector means.